Nonpulsating internal-combustion heater



NWPZ 190 I H. .3. DE N. McCQU-UM 2,452,78

NONYULSATING INTERNAL-COMBUSTION HEATER 3 Sheets-Sheet 1 Filed March 6, 1943 Nov. 2, 1 948.

3 Sheets-Sheet 2 Filed March 6. 1943 3 Sheets-Sheet 3 H. J. DE N; MCQLLUM NONPULSATING INTERNAL-COMBUSTION EEATER Nov. 2, 1948.

Filed March 6, 1943 Patented Nov. 2, 1948 NONP'ULSATING INTERNAL-COMBUSTION HEATER.

Henry J. De N. McCollum, Chicago, 111.: Thelma McCollum, executrlx oi said Henry .I. Do N. Mc- Coilum, deceased, minor to Stewart-Warner Corporation, Chicago, in, a corporation oi Virginia Application March 8, 1943, Serial No. 478,259 11 Claims. (01. 126-116) My invention pertains to heaters and more particulariy to heaters oi the internal combustion type especially adapted for, but not limited to,

use in aircraft.

In internal combustion heaters, it has been common practice to provide a muiiier for silencing or reducing the noise of operation of the heater. Such mumer ordinarily consists of a metal shell containing glass wool or stainless steel wool which is in communication with gases issuing from the combustion chamber by way of a multiplicity of openings in the muiiler shell whereby sound can enter the interior of the shells through these openings and be absorbed by the glass wool or stainless steel wool therein. In such heaters the sound absorbing material in the muiiler shell deteriorates rapidly and an object of my inven tion is to provide a heater in which such rapid deterioration is avoided.

Another object of my invention is to provide a heater which minimizes such explosions as may occur when the heater is first started and which result from the presence of combustible mixture in the gas passages of the heater and in exhaust pipes connected thereto.

Another object of my invention is to provide a new and improved mufiier which has alonger life than the mufllers heretofore in use.

Another object of my invention is to provide a heater having a new and improved muiiler mounting whereby the muflier may be readily removed and replaced.

Another object of my invention is to provide a new and improved muflier particularly designed to absorb explosions occurring in the heater.

Other objects and advantages will become apparent as the description proceeds.

In the drawings:

Fig. 1 is a longitudinal, sectional view of a heater embodying a preferred form of my invention;

. Fig. 2 is a partial, lon itudinal, sectional view taken on the line 2-2 of Fig. 1;

I an air inlet Hi connected to a ram, blower or any other suitable means which supplies all of the ventilating and combustion air required by the 2 heater. 'Ihe inlet I0 is connected to one end of a cylindrical casing i2 enclosing a. combustion chamber I4 discharging products of combustion into one end or a cylindrical heat exchanger it to which the combustion chamber is attached as by studs ii. The hot gases issuing from the combustion chamber flow into the leithand ends of gas passages 29 provided by the heat exchanger and are discharged from the righthand ends of these passages into an outlet chamber it from which the current gases flow through an exhaust pipe 24 leading to atmosphere. In conventional aircraft practice, the exhaust pipe discharges outside oi the fuselage oi the aircraft and the outlet end of this pipe is so arranged that suction is created thereat by the normal operation of the aircraft.

Referring more particularly to Figs. 3 and s, it

will be seen that the heat exchanger it comprises a corrugated sheet metal tube 26 supporting longitudinally extending fins 28 whose outer edges are divided into fingers by slots 30 best shown in Fig. 1. The air entering the lefthand end of the casing l2 absorbs heat from the fins 28 and most of this heated air flows from the righthand end of the casing I2 into a duct at leading to the aircraft cabin or one or more other spaces to be heated.

A portion of the heated air is used for combustion purposes and enters the inlet 34 of a combustion air pipe 35 leading to a carburetor 3B, com

prising the usual float bowl 40 and Venturi tube 42. A pipe 44 connects the float bowl 40 with any suitable source of fuel and fuel from the float bowl is delivered to the throat of the Venturi tube 42 by a Jet 46 to form a mixture of fuel and air which passes into an induction tube 48 attached to the outlet end of the Venturi tube. The induction tube 48 is preferably of uniform diameter and has a smooth interior free from obstructions or interruptions and conducts the fuel and air mixture to the combustion chamber M.

This induction tube has a preheating portion 50 located in and curved about the axis of the circular wall I52 of the combustion chamber and terminating in an outlet 54 which discharges a combustible mixture tangentially of the wall 52 whereby the combustible mixture whirls about the axis of the combustion chamber. This-mixture is ignited by an electrical igniter 66 located in a cylindrical pocket 58 at one side of the combustion chamber and connected to this chamber by way of an inlet 60 and an outlet 82.

The heat exchanger and combustion chamber are shown as being supported in the casing It by brackets 04 which constitute a suitable arrangemcnt or attaching these parts together, although any her suitable attaching means may be substituted therefor. The heater, as thus la:- described, is identical with that disclosed in my copending application, Serial No. 478,258, filed March-6, 1943, which has become Patent No. 2,417,604 granted March 18, 1947, and is claimed in that application or the earlier applications referred to therein.

A mufiler 00 is located in the heat exchanger II and is illustrated as comprising a sheet metal, cylindrical shell 80 of suitable size to slide into this heat exchanger. The ends of the muflier shell are closed by sheet metal cups I0 and I2 which are welded or otherwise secured to the shell 00 in such manner as to prevent any gas from seeping between these discs and the shell 00. The disc I! is provided with a pin 14 having a reduced threaded end I0 extending through a sleeve 18 welded or otherwise secured in a Wall of' the exhaust pipe 24. A nut 80 is attached to the threaded and I0 of the pin I4 and serves to hold the muffler in assembled position in the heat exchanger I0.

The lefthand end of the muiller is exposed to the heat created in the combustion chamber I0 and to the hot gases issuing therefrom. I have found that the intense heat to which this end of the muilier is exposed causes rapid deterioration of glass wool and a somewhat slower deteri-' oration of stainless steel wool and in order to reduce or eliminate completely such deterioration I provide this end of the muffler with an insulating plate 82 of fire clay, or other suitable material. This 'fire clay, or other heat insulating material, is molded or otherwise formed into a plate of just the right size and shape to be rethrough the glass or steel wool contained therein and produces rapid deterioration ,of this sound absorbing material. A feature of my present invention lies in the provision of means for pre-w venting such flow of gas through the sound absorbing material of the muifler.

The muiiier 08 is divided into-a plurality' of compartments 80 by partitions 90 which are welded or otherwise secured to the shell 88 in such manner that seepage can not occur between the edges of the partitions 90 and this shell. Each of the compartments 88 is filled with glass wool or stainless steel wool, or other suitable sound absorbing material 89, which communicates with the gas passages through a single circumferential row of openings 92, illustrated as being located centrally of the compartments 88. In the heater shown in Figs. 1 to 4, inclusive, deterioration of the sound absorbing material 00 is exceedingly slow and the heater is capable of giving long and trouble-free service without muiiler replacement. When and if it is desirable to replace the muiiier, the muiller may be readily slipped out of either end of the heat exchanger after the heater has been disassembled sumciently to permit such removal.

In Figs. 5 and 6, I have shown a heater embodying a modified form of my invention which is particularly adapted to cushion such explosions as may occur in the heater when it is first started and which are due to the presence of combustible mixture in the gas spaces of the heater and exhaust pipe attached thereto. Cushioning of these explosions reduces noise and the possibility of injury to the heater and permits the heater to be made of lighter material and thus reduces the total weight of the heater.

The heater of Figs. 5 and 6 is identical with the heater of Figs. 1 to 4, inclusive, except as tothe construction of the muiller. The heater of Figs. 6 and 6 has a muiiler 100 comprising a cylindrical sheet metal shell I02 having discs I04 and I00 welded or otherwise secured 'to the ends thereof. A central partition I08 divides the muifler into a pair of compartments H0 which are shown as being of equal size, but, if desired, the partition I08 may be placed nearer either end of the muiiler so that the acoustic properties of the compartments IIO will vary and will absorb diiferent sounds associated with the inlet and outlet ends of the heaters respectively:

The discs I 04 and I 00 are provided with perforations H2 for admitting sound to the compartments H0. The partition I08, however, is imperforate and forms a gastight seal with the shell I02 to prevent-any flow or seepage of gas from one compartment to the other. The compartments IIO are filled with stainless steel wool or glass wool, or other suitable sound absorbing material indicated at III.

Since each compartment H0 has only a single set of perforations connecting this compartment with a gas passage, there is no tendency for gas "protected against deterioration by contact with 'steel'wool has the higher melting point and is less ail'ected by intense heat.

The lefthand compartment I I0 has restricted communication with the combustion chamber I4 and the gas passages adjacent thereto. If, upon starting the heater, or at any other time. an explosion should occur in this chamber or the ad- Jacent gas passages, the explosive 'force would be partially absorbed and minimized by flow through perforations H2 into the lefthand compartment 0. Since this compartment would contain practically no combustible mixture, no explosion would occur in this compartment and at the time of the explosion the compartment would be at normal operating pressure, that is,

' slightly below atmospheric pressure and would constitute 'a cushion for the exploding gases.

The rlghthand compartment IIO has similar restrictive communication with the outlet cham ber 22 and exhaust pipe 24 and would serve as a means for cushioning the eil'ect of any explosion occurring therein. In addition to cushioning or minimizing the force of explosions in the heater, the compartments H0 and sound absorbing material contained therein reduce the noise occasioned by the explosion and prevent the occupants of the aircraft from becoming unduly alarmed.

In each of the two heaters illustrated in the drawings, provision is made for preventing gas flow through the sound absorbing material of the muiiler and for thereby increasing the useful life of this material. The particular number, size and arrangement and other details of the muiiler compartments can, of course, be varied to suit particular conditions. Likewise my novel muiiier. is not limited to use in the particular design of heater shown in the drawing, but may be used in other heaters of the internal combustion type or which utilize gases capable of destroying the sound absorbing material if permitted to flow therethrough. It is to be understood that my invention is not limited to the details shown and described, but may assume numerous other forms and that the scope of my invention is defined in the following claims.

I claim:

1. A heater of the class described comprising a cylindrical heat exchanger which includes conduit means for hot gases extending from end to end and opening laterally toward the axis of the heat exchanger, means forming a combustion chamber at one end thereof for supplying hot gases to said conduit means oi the heat exchanger, a casing enclosing said heat exchanger, means for supplying air to said casing to be heated by passing over said heat exchanger, means for supplying a combustible mixture to said combustion chamber, a muiher located in said heat exchanger and comprising a cylindrical shell shorter than the heat exchanger and fitting snugly therein to form an inner'wall thereof spaced from both ends of the heat exchanger to provide access for hot gases thereto and therefrom and having one end adjacent said combustion chamber, a plurality of imperforate discs dividing said shelLinto a plurality of sound absorbing compartments, sound absorbing material located in said compartments, a single row of openings in said shell for each compartment providing acoustic coupling with the conduit means. and means to anchor said mufiler against endwise movement in said heat exchanger.

2. A heater of the class described comprising a tubular heat exchanger, means forming a combustion chamber removably attached to one end thereof, an exhaust. pipe removably attached to the opposite end of said heat exchanger, a muffler located in said heat exchanger and slidable lengthwise thereof, said muiiler comprising a cylindrical shell closely fitting in said heat exchanger and supported thereby, said shell containing sound absorbing material acoustically coupled to. said combustion chamber by openings in said shell, a pin projecting from one end of said muiller, and means-for detachably connecting said pin to said exhaust pipe to prevent sliding movement of said muiller relative to said heat exchanger.

3. A heater of the class described, comprising a cylindrical heat exchanger, means forming a combustion chamber for supplying hot gases to one end of said heat exchanger, 8. gas exhaust pipe connected to the other end of said heat exchanger, and a muilier located in said heat exchanger, means dividing said muilier into separate explosion, cushioning and sound absorbing compartments, restricted openings disposed in a single diametricai plane transverse to the muiiier and providing communication between one of said compartments and the said combustion chamber,

restricted openings disposed in a single diametrical plane transverse to the muffler and providing communication between another of said compartments and said exhaust pipe and a sound absorbing material in said compartments.

4. A heater of the class described, comprising a cylindrical heat exchanger, means for supplying hot gases to one end of said heat exchanger, an exhaust pipe communicating with the other end of said heat exchanger, a mufller interposed between said means and said exhaust pipe, said murder comprising a plurality of compartments, a perforated end for said muiller ailording limited communication between said means and one of said compartments, 9, second perforated end for said muiller affording limited communication between said exhaust pipe and another of said compartments, sound absorbing material in said compartments, and means for directing air over said heat exchanger.

5. A-heater of the class described comprising a tubular heat exchanger, means forming a combustion chamber for supplying hot gases to one end of said heat exchanger, an exhaust pipe for receiving said gases from the other end of said heat exchanger, and a mufiler located in said heat exchanger, said mufiler comprising a shell, a, gas-proof partition dividing said shell into two compartments, a perforated end for said shell adjacent said combustion chamber and providing restricted communication between said chamber andone of said compartments, 9, second perforated end for said shell adjacent said exhaust pipe and providing restricted communications between said exhaust pipe and the other of said compartments, and sound absorbing material in said compartments.

6. A heater of the class described comprising a tubular heat exchanger having a corrugated wall forming inwardly open channels extending longitudinally thereof, means including a combustion chamber at one end of said heat exchanger for supplying hot gases to one end of said channels, a muiiler located in said heat exchanger and having a, cylindrical shell shorter than the corrugated well. said shell being fitted snugly within said corrugated wall and spaced from both ends thereof to provide access to and from the said channels, gastight means dividing said shell into compartments arranged in end-to-end relation lengthwise of the muifier shell, each'of said compartments having a series of openings acoustically coupling said channels with the interior oi the shell. the openings in any compartment lying in a substantially common plane diametricaly disposed with respect ,to the shell, and a sound absorbing material in said compartments.

7. A heater oi the class described comprising a tubular heat exchanger having a corruga ed wall forming inwardly open channels extending longitudinally thereoi, means including a combustion chamber at one end of said heat exchanger for supplying hot gases to one end of said channels, a muiller located in said heatexchanger and having a cylindrical shell extending adjacent the open sides of the channels and direc ing said hot gases along said channels, said mufiler shell having closed ends, gas-tight partition means dividing said shell into a plurality of compartments, each of said compartments having a series of openings through the shell acoustically coupling the compartments to said channels, the openings,

in any one compartment being positioned at points subject to a pressure variable from time to time but of the same magnitude at each of said openings at any given time when the heater is operating and a sound absorbing material contalned in each or said compartments.

8. A heater of the class described comprising a tubular heat exchanger having inwardly open gas channels extending longitudinally thereof, means including a combustion chamber in direct communication with said heat exchanger for supplying hot gases to one end of said channels, a mu!- fler located in said heat exchanger and directing said hot gases along said channels, said muiiier comprising a sheet metal shell having closed'ends, oneor more gas-t ght partitions dividing said shell into a plurality of compartments. and a sound absorbing material in each oi said compartments, each compartment having a series of openings in the shell acoustically coupling said compartments with said gas channels, the openings in any one compartment being positioned at points on the shell subject to a pressure variable from time to time but of the same magnitude at each of said openings at any given time when the heater is operating.

9. A heater of the class described comprising a heat exchanger having inwardly open longitudinally extending gas channels on the inner periphery thereof, means forming a combustion chamber in direct communication with one end otsaid heat exchanger tor supplying hot gases of combustion to, said channels, means directly communicating with the opposite end of said heat exchanger and forming an outlet for exhausting said gases. a muiiier concentrically disposed in said heat exchanger and confining to said channeis the flow of hot gases from said combustion chamber to said exhaust outlet, means forming a. plurality of compartments arranged in end to end relation lengthwise of said muilier, each compartment being sealed against direct communication with an adjacent compartment and having a series of openings providing acoustic coupling between each compartment and the hot gases, the openings in any one compartment being positioned at points in the wall thereof subject to a pressure variable from time to time but of the same magnitude at each of said openings at any given time when the heater is operating, a sound absorbing material contained in said compartments, and means for directing ventilating air over said heat exchanger.

10. A heater or the class described comprising a. heat exchanger, means forming a combustion chamber in direct communication with one end of combustion thereto. means directly communieating with the opposite end or said heat exchanger and forming an outlet for exhausting said gases, a muilier concentrically disposed in said heat exchanger, means forming a series of gas passages between said heat exchanger and of said heat exchanger for supplying hot gases muifler connecting said combustion chamber and outlet, means forming a plurality of separate noncommunicating compartments arranged in end to end relation lengthwise of said heat exchanger, means for protecting one end or said muiiier from the heat or said combustion chamber, means for attaching the other end of said muiller to said heat exchanger, means providing acoustic coupling between each of said compartments and said hot gas passages, the acoustic coupling means for any one compartment being positioned at points in the wall thereof subject to a pressure variable from time to time but 01 the same magnitude at any given time when said heater is operating, a sound absorbing material in each of said compartments and means for directing air over said heat exchanger.

11. A heater or the class described comprising a heat exchanger, means forming a. combustion chamberin direct communication with one end of said heat exchanger for supplying hot gases of combustion thereto, means directly communicating with the opposite end 0! said heat exchanger and forming an outlet for exhausting said gases, a mui'iler concentrically disposed in said heat exchanger to form gas passages connecting said combustion chamber and outlet, means forming a plurality of noncommunicating compartments in said muiller disposed in end to end relation lengthwise of the muiiler, each of said compartments having a circumferentially arranged series of openingsin the walls thereof coupling the compartments acoustically to said hot gas passages, the openings in any one compartment being positioned at points in the walls thereof subject to a pressure variable from time to time but of the same magnitude at each of said openings at any given time when the heater is operating, sound-absorbing material in said compartments, and means at the end of said muiiler adjacent said combustion chamber for protecting said soundabsorbing material from the hot gases formed in the combustion chamber.

HENRY J. DE N. McCOLLUM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS McCollum June 26, 1945 

